Various types of petroleum-derived hydrocarbon oils undergo deterioration on storage or upon exposure to severe conditions. Thus fuel oils such as gasoline, diesel fuel, jet fuel, other aviation fuel, burner oil, furnace oil, kerosene, and naptha, for example, and other oils such as lubrication oils, cutting oils, slushing oils, etc., undergo deterioration as evidenced by such changes as, for example, formation of sediment and discoloration.
Sediment formation is undesirable for various reasons. When formed in tanks storing hydrocarbon oils the settling of accumulated particles requires periodic draining and cleaning of storage tanks, leading to temporary unavailability to storage capacity, substantial diversion of manpower, and waste disposal problems. Sediment formation in burner oil tends to plug strainers, burner tips, injectors, etc. In diesel fuel such sediment tends to form sludge and varnish in the engine. If the oil is used as a heat exchange medium, as for example with jet fuel, the sediment tends to plug exchanger coils. In gasoline the sediment may tend to deposit on sensitive parts in an internal combustion engine, such as carburetors, thereby decreasing the efficiency of combustion and causing increased fuel consumption.
It is apparent, therefore, that reduced sediment formation in hydrocarbon oils is desirable. One method of effecting such reduction would be to eliminate, to a substantial degree, those processes leading to particulate formation, such as oxidation. Another method would be to prevent agglomeration and/or settling of the formed particulate matter by effectively maintaining the fine particulates in a well dispersed state, for when the particulates are so dispersed the aforementioned difficulties associated with sediment formation either do not occur or are of substantially lessened severity.
Discoloration of hydrocarbon oils is undesirable because it is an indication that degradation has occurred or is occurring, hence there is a marked customer preference for lighter oils. Thus there is an economic incentive for minimizing discoloration and degradation of hydrocarbon oils, especially during long-term storage.